1. Field of the Invention
The invention is directed to an improved fuel injection system for an internal combustion engine of the type having a high pressure pump and a fuel injector for each cylinder of the engine.
2. Description of the Prior Art
One fuel injection system of the type with which this invention is concerned is known from European Patent Disclosure EP 0 957 261 A1. For each cylinder of the engine, this known fuel injection system has one high-pressure fuel pump and one fuel Injection valve communicating with it. The high-pressure fuel pump has a pump piston, which is driven in a reciprocating motion by the engine and which defines a pump work chamber that communicates with a pressure chamber of the fuel injection valve. The fuel Injection valve has an Injection valve member, by which at least one injection opening is controlled, and which is movable by the pressure prevailing in the pressure chamber in an opening direction counter to a closing force. By means of an electrically controlled control valve, a communication of the pump work chamber with a relief chamber is controlled in order to control the fuel injection. When the pressure in the pump work chamber and thus in the pressure chamber of the fuel injection valve reaches the opening pressure, the injection valve member moves In the opening direction and uncovers the at least one injection opening. The injection cross section that is controlled by the injection valve member in the process is always the same size. This does not enable optimal fuel injection under all engine operating conditions.